In an aircraft, a plurality of electronic units are often mounted or stored in an avionics bay or rack. While some electronic units are permanently mounted within the avionics bay, other electronic units may be portable such that the units can be removed from the bay and transported to and from the aircraft, such as the well-known aircraft “black box.” These portable or plug-in electronic units must be operatively connected to a supply of power and plugged into the central control system of the aircraft in operation. Consequently, a plurality of avionics equipment mounting trays is provided in the avionics bay of an aircraft. The avionics equipment mounting trays include a support structure for holding the portable electronic unit and a mating wire harness or plug for plugging a portable electronic unit into a system and enabling communication between the portable electronic unit and the central control system. The portable electronic unit must have a reliable connection with the mating wire harness or plug to ensure proper operation of the avionics equipment in the portable electronic unit. As may be appreciated, an active avionics environment provides various vibration, shaking, and other similar forces on the units plugged into an avionics bay. Therefore, the connection of a unit into operation with the central system must be robust.
To provide a robust and reliable connection between the portable electronic unit and the mating wire harness, a hold-down assembly may be provided on the avionics equipment mounting tray. The hold-down assembly includes a locking collar that engages with a portion of a housing of the portable electronic unit. The locking collar applies a force to the portable electronic unit to ensure engagement of the portable electronic unit with the mating wire harness.
When an aircraft operates, a high amount of vibration is imposed on the portable electronic units and the avionics equipment mounting trays. This vibration can force conventional hold-down assemblies to loosen from engagement with the portable electronic unit. The portable electronic unit can then become disengaged with the mating wire harness, thereby affecting the proper operation of the avionics equipment. Thus, it would be desirable to provide a hold-down assembly that resists typical vibration forces from aircraft operation while applying an appropriate force to hold the portable electronic unit in position on the avionics equipment mounting tray.